Theoretical predictions of MB₅N₅: Atom-stuffed boronitride clathrate cages derived from the high-pressure superhydrides

This study investigates 198 MX₅Y₅ (X, Y = B, C, or N) clathrate-like structures derived from MH₁₀ superhydrides using high-throughput Density Functional Theory (DFT) geometry optimizations and phonon calculations. A wide variety of electropositive and electronegative encapsulated atoms were considered. From all of the studied systems only 34 MB₅N₅ phases were found to be dynamically stable at ambient pressure. The highest 1-atmosphere superconducting critical transition temperature was predicted for FB₅N₅. However, ab initio molecular dynamics simulations revealed that all of the identified superconducting phases decompose by 300 K at 1 atm, while only eleven semiconducting phases remained thermally stable. Our findings underscore the critical role of kinetic and thermal stability in predicting viable superconductors. The electronic structure of the MB₅N₅ compounds were rationalized in terms of electron donating and withdrawing intercalants. DFT and machine-learning based predictions of their mechanical properties were compared with those of an empty boronitride cage.